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img{
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    <h1>图像透明度</h1>
    <p>opacity 属性规定元素的透明度。值越低，越透明：</p>
    <p>50% 不透明度的图像：</p>
    <img src="../w3logo-1.png" 
    alt="Tulip" width="600" height="400">
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